Controlling Long-Range Genomic Interactions at a Native Locus by Targeted Tethering of a Looping Factor

SummaryChromatin loops juxtapose distal enhancers with active promoters, but their molecular architecture and relationship with transcription remain unclear. In erythroid cells, the locus control region (LCR) and β-globin promoter form a chromatin loop that requires transcription factor GATA1 and the associated molecule Ldb1. We employed artificial zinc fingers (ZF) to tether Ldb1 to the β-globin promoter in GATA1 null erythroblasts, in which the β-globin locus is relaxed and inactive. Remarkably, targeting Ldb1 or only its self-association domain to the β-globin promoter substantially activated β-globin transcription in the absence of GATA1. Promoter-tethered Ldb1 interacted with endogenous Ldb1 complexes at the LCR to form a chromatin loop, causing recruitment and phosphorylation of RNA polymerase II. ZF-Ldb1 proteins were inactive at alleles lacking the LCR, demonstrating that their activities depend on long-range interactions. Our findings establish Ldb1 as a critical effector of GATA1-mediated loop formation and indicate that chromatin looping causally underlies gene regulation.PaperFlick To view the video inline, enable JavaScript on your browser. However, you can download and view the video by clicking on the icon belowHelp with MP4 filesOptionsDownload video (50378 K)

Graphical AbstractFigure optionsDownload high-quality image (149 K)Download as PowerPoint slideHighlights
► Chromatin loops can be generated by targeted tethering of select looping factors
► Forced juxtaposition of a distant enhancer and promoter can trigger transcription
► Ldb1 functions as a looping factor
► Chromatin looping could be used to regulate genes for therapeutic intervention